(a) Field of the Invention
The present invention relates to a field stop operating mechanism for microscopes.
(b) Description of the Prior Art
Among known illumination systems for microscopes, there is an illumination system arranged to deflect its optical axis O, which passes in the inside of a base 4, at the right angle by means of a reflecting mirror 1 as shown in FIG. 1 and to thereby direct the light from a light source, which is not shown in the figure, upwardly by the reflecting mirror 1 toward a condenser lens. In such illumination system, a field stop 2 and a window lens means 3 are arranged in front and rear of the reflecting mirror 1 and, moreover, the field stop 2 is arranged in the middle portion of the base 4. In case of a microscope having such illumination system, an operating ring 6 is integrally fixed to a rotating ring 5 as shown in FIG. 2, a lever 6a of the operating ring 6 is projected upward beyond the top surface of the base 4, and the field stop 2 is stopped down and opened by operating the lever 6a. However, the above-mentioned field stop operating mechanism has disadvantages as described below. That is, as the lever 6a is located at a deeper position (position on the right in FIG. 1) when seen from the position of the person who operates the microscope and, moreover, the window lens means 3 exists on this side (left side in FIG. 1) of the lever 6a. Therefore, it is inconvenient to operate the lever 6a. Besides, a gap exists at the portion where the lever 6a of the operating ring 6 is projected from the base 4, and it is difficult to stop up the gap. Consequently, dust and the like tend to enter the inside of the illumination system through the gap.